All About Pocket Knives

Anyone have any idea what the groove on the backside handle is for? I though nail puller or just a way to hang it on a tool board, but I don't think either of those are right. You could hang it from a tool board with the bail and I don't think there is enough leverage for a nail puller. Not my knife - saw it in an auction.

The slot(s) on the handle is what they call a "shackle key". Used to tighten or loosen the shackle bolts on a sailing boat.

Disclaimer: I'm not a smart man, nor am I a sail boating dude. I only know this because I got lucky in searching for the answer myself. Your question piqued my interest too. And now we know the rest of the story.

Thank you. Now that you have answered the question, I feel certain I have seen that on other knives.